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Abstract:

Lipids and oils, integral components of cosmetic products, exist in a number of intermediate physical states, or mesomorphic phases, between the crystalline solid and isotropic liquid. The stability of these phases depends on temperature and composition, and each lipid's pattern of dependency is conveniently described in the form of an isobaric (constant pressure) temperature-composition phase diagram. Such diagrams are of great utility in guiding the choice of formulation ingredients for inclusion in cosmetic products and for obviating such manufacturing problems as caking and immiscibility. This paper describes two new and related methods of collecting mesomorphic phase information which are less time-consuming and more efficient than conventional techniques. By incorporating a range of conditions into each sample preparation?a temperature gradient in the first method and a lyotrope gradient in the second?and utilizing a new method of phase identification called time-resolved x-ray diffraction, the time required to collect phase information for a complete diagram is reduced to minutes. Temperature-composition phase diagrams constructed using these methods compare well with those constructed by conventional means